Question NoFollow attribute being used on internal links to Forum Categories and Topics

NoFollow also really shouldn't be used this way. If some other website links to the forum topic using the incorrect link and doesn't include a nofollow then Google will find the page anyways. From Wikipedia:
"nofollow is a value ... to instruct search engines that the hyperlink should not influence the ranking of the link's target in the search engine's index."
On Google's help page there is no mention of using nofollow to combat duplicate content: support.google.com/webmasters/answer/96569?hl=en

If people are worried about duplicate content then Google recommends using canonical urls
support.google.com/webmasters/answer/139066?hl=en
Basically this includes a html element to the proper page. Here is a quote from Wikipedia:
"A canonical link element is an HTML element that helps webmasters prevent duplicate content issues by specifying the "canonical" or "preferred" version of a web page[1][2] as part of search engine optimization. It is described in RFC 6596, which went live in April 2012."

if you use canonical, then the page isn't indexed, so the same issue.
But on the next version we have some improvements like meta robots on the topic itself. based on your joomla global setting.

But you don't want the page indexed with a different url because of duplicate content issues. The canonical page will be the only indexed page.
For example the page:
www.kunena.org/forum/k5-0-support/138179...es-and-topics/unread
canonical url would be:
www.kunena.org/forum/k5-0-support/138179...ategories-and-topics
A forum creates interesting issues regarding duplicate content etc.. since there are so many ways of displaying the content.

unread are only visible by logged in users, not for bots. But for the next version we have some improvements. Please wait for the next release

will add canonical on unread urls

Right, my mistake. Google would never see that url. I was just using it as an example of a different url with similar content.
Looking forward to the next release.